6 Apr
2009
6 Apr
'09
11:24 p.m.
I think the regulator is a 54-09728 or 54-09827, and they were used ia lot
of DEC items.
Paul
On Mon, Apr 6, 2009 at 3:59 PM, Tobias Russell <toby at coreware.co.uk> wrote:
Thanks Tony,
Yes pretty sure its a bridge rectifier as I found H740 schematics plus
opened up my other 8-M which I now realise has essentially the same
power supply. I guess DEC just made slight design revisions plus
reposition the supply in order to solve the unreliability of these
earlier units.
Studying the schematic further I've found NSS-3514 annotated next to the
rectifier (sorry missed this when I first looked through it) so I'll see
if I can hunt down this part. If not I'll try the diode approach
Thanks,
Toby
On Mon, 2009-04-06 at 21:00 +0100, Tony Duell wrote:
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One is a
DEC 1110714 bridge rectifier and the other is a MJ900
transistor. I think I've sourced the MJ900 but can't find anywhere
stocking the 1110714.
Does anyone know an alternative non-DEC part number for the rectifier?
Are you sure it's a _bridge_ rectifier? I thought you said it was a TO3
can, DEC often used a double-diode in that case (common cathode to the
case, anode to the 2 pins -- sort of a semiconductor version of an EZ80
:-)) as a biphase full-wave rectifier with a centre-tapped transformer
winding.
In any case it should be fairly easy to get some diodes with sufficient
forward courrent capacity (and enough PIV -- rememebr this is _twice_ the
peak voltag from the transformer!) to do the job and just wire them up
appropritately. There should be enough spave in a PDP8/M PSU to fit them
in. It may not look original, but it'll get the machine going and you can
always fit the original part if you find one.
-tony